if语句的使用
在Python中，要构造分支结构可以使用if、elif和else关键字。所谓关键字就是有特殊含义的单词，像if和else
需要说明的是上面代码中的range类型，range可以用来产生一个不变的数值序列，而且这个序列通常都是用在循环中的，例如：
-
range(101)可以产生一个0到100的整数序列。 -
range(1, 100)可以产生一个1到99的整数序列。 -
range(1, 100, 2)while循环
如果要构造不知道具体循环次数的循环结构，我们推荐使用
while循环。while循环通过一个能够产生或转换出bool值的表达式来控制循环，表达式的值为True循环继续，表达式的值为False循环结束。下面我们通过一个“猜数字”的小游戏（计算机出一个1~100之间的随机数，人输入自己猜的数字，计算机给出对应的提示信息，直到人猜出计算机出的数字）来看看如何使用while循环。
a,b,c=map(float,input('Enter a,b,c:').split(','))
sum = b**2 - 4*a*c
r1=(-b+sum**0.5)*0.5
r2=(-b-sum**0.5)*0.5
if sum > 0:
print("The roots are {0} and {1}".format(r1,r2))
elif sum < 0:
print("The root is {0}".format(-b * 0.5*a))
else:
print("The equation has no real roots")
import random
answer1 = random.randint(1,100)
answer2 = random.randint(1,100)
number = float(input("输入整数的和：>>>>>"))
sum=answer1+answer2
if number == sum:
print("Ture")
else:
print("False")
city = ['星期日','星期一','星期二','星期三','星期四','星期五','星期六']
Today = int(input('Today is :'))
num_day = int(input('Number of days :'))
day = num_day%7
if (Today+day)<7:
print('Future day is: %s'%city[Today+day])
if (Today+day)==7:
print('Future day is: %s'%city[0])
if Today+day>7:
print('Future day is: %s'%city[Today+day-7])
num1,num2,num3 = eval(input("输入三个整数："))
if num1 > num2 > num3:
print(num1,num2,num3)
if num1 > num3 > num2:
print(num1,num3,num2)
if num2 > num1 > num3:
print(num2,num1,num3)
if num2 > num3 > num1:
print(num2,num3,num1)
if num3 > num2 > num1:
print(num3,num2,num1)
if num3 > num1 > num2:
print(num3,num1,num2)
weight,packsge=eval(input("输入重量和价格："))
weight_1,packsge_1=eval(input("输入重量和价格："))
sum1 = packsge / weight
sum2 = packsge_1 / weight_1
if sum1 > sum2:
print("2")
else:
print("1")
mounthy,year=eval(input("输入月和年："))
if year % 4 == 0 and year % 100 !=0 or year % 400 ==0:
if mounthy == 2:
print("29")
elif mounthy == 4:
print("30")
elif mounthy == 6:
print("30")
elif mounthy == 9:
print("30")
elif mounthy == 11:
print("30")
else:
print("31")
else:
if mounthy == 4:
print("30")
elif mounthy == 6:
print("30")
elif mounthy == 9:
print("30")
elif mounthy == 11:
print("30")
else:
print("31")
import numpy as np
res = np.random.choice(['正面','反面'])
my = input("正面，反面：")
if my in '正面，反面':
if my == res:
print("正确！")
else:
print("错误！")
print(my)
print(res)
import numpy as np
res = np.random.choice(['0','1','2'])
my = input("0，1，2：")
if my in '0，1，2':
if my == "0":
if res == "0":
print("over")
elif res == "1":
print("res win")
elif res == "2":
print("my win")
if my == "1":
if res == "0":
print("my win")
elif res == "1":
print("over")
elif res == "2":
print("res win")
if my =="2":
if res == "0":
print("res win")
elif res == "1":
print("my win")
elif res == "2":
print("over")
print("电脑出：",res)
print("我出：",my)
import math
year,m,q=map(int,input('请输入年月日【逗号隔开】').split(','))
j=math.floor(year/100)
k=year%100
h=(q+math.floor(26*(m+1)/10)+k+math.floor(k/4)+math.floor(j/4)+5*j)%7
week=['星期六','星期日','星期一','星期二','星期三','星期四','星期五']
print('Day of the week is %s'%week[h])
import numpy as np
res = np.random.choice(['A','2','3','4','5','6','7','8','9','10','j','q','k'])
my = np.random.choice(['梅花','红桃','方块','黑桃'])
if my in '梅花，红桃，方块，黑桃':
if my == "梅花":
print(my+res)
if my == "红桃":
print(my+res)
if my == "方块":
print(my+res)
if my == "黑桃":
print(my+res)
number=float(input("一个三位数："))
ge = int(number %10)
shi = int(number /10%10)
bai = int(number /100)
if ge == bai:
print("{0}是回文数！".format(number))
else:
print("不是回文数！！！")
a,b,c=eval(input("三个数:"))
if a + b >c and b + c > a and a + c > b:
sum=a+b+c
print(sum)
else:
print("三边不合法")
今天学习分支结构和循环结构